1. Field of the Invention
The present invention relates to a plasma arc torch and, more particularly, to a plasma arc torch with improved safety provisions.
2. Description of Related Art
Blowback type plasma torches are generally configured such that an electrode and a nozzle can be brought into contact with each other to ignite an arc, whereafter, the electrode is separated from the nozzle so as to draw the arc therebetween. A fluid, such as air, is concurrently provided under pressure through the nozzle, wherein the air flow interacts with the drawn arc so as to form a plasma. The plasma flowing through the nozzle is then directed at a workpiece to perform a cutting function.
In some instances, the fluid for forming the plasma can also be used to separate the electrode from nozzle, so as to cause the electrode to move between a torch inoperative position (in contact with the nozzle) to a torch inoperative position (separated from the nozzle to allow the arc to be drawn therebetween). That is, the formation of the plasma generally requires a limited amount of, for example, air. As such, the remainder of the fluid can be used for other purposes, such as to separate the electrode from the nozzle and allow the arc to be drawn. Using the excess air for providing such a “blowback” operation of the electrode may provide, for example, a relatively compact size, with respect to both the components and the overall assembly, and longer service life of the torch components due to, for instance, less complex torch systems and fewer components.
However, another consideration with these torches is safety, since the torch must incorporate a power feed for providing the arc. That is, in some instances, a blowback-type plasma torch may incorporate consumables, associated with the electrode, that must be periodically replaced or otherwise maintained, wherein servicing the consumables may require disassembly (and subsequent reassembly) of the torch, possibly with hazardous exposure to the power feed. Such consumables, though, may be implemented into the torch in different ways so as to attempt to reduce the risk of accidental exposure to the power feed to the torch. For example, a torch may incorporate a set of electrical contacts in the torch head, wherein installation of a final consumable component bridges or otherwise completes a circuit and allows a signal current to flow to the electrode. This type of configuration, however, relies only on the electrical contacts in the relatively harsh environment of the head of a plasma torch, which may have a detrimental effect on the reliability of such an arrangement with respect to operation of the torch. Further, the electrical circuit may still be live in the torch during disassembly and reassembly procedures, or if the torch is incompletely or improperly reassembled, and thus this configuration may not effectively eliminate the risk of exposure to the power feed.
In another example, an electrical sensor/switch may be incorporated into the blowback-type torch to sense the position of the movable component within the torch body. Proper assembly of the consumables in turn moves the movable component into the torch body, thereby activating the sensor/switch and allowing current to flow to the electrode. However, this type of configuration typically requires additional wiring and/or componentry in the torch head, which may undesirably increase the size/weight of the torch. In addition, these extra components are also exposed to the harsh plasma torch environment, and thus may be detrimental to torch reliability. This configuration may also allow the electrical circuit to be live in the torch during disassembly and reassembly procedures, or if the torch is incompletely or improperly reassembled, and thus may not effectively eliminate the risk of exposure to the power feed.
Thus, there exists a need for a plasma arc torch, particularly a blowback type of plasma arc torch, having improved safety provisions, for example, by providing components configured to be formed into a torch assembly in a precise, simple, and consistent manner. Such a torch should also require complete and/or proper assembly, upon initial implementation or following required maintenance, prior to electrical and/or air service being provided thereto so as to further facilitate safety, wherein such safety provisions should not adversely affect the reliability or compactness of the torch.